The invention relates generally to clearance measurement systems, and more particularly to, a multi-range clearance measurement system for measuring a clearance between a stationary component and a movable component of a rotating machine.
Various types of sensors are known and are in use in different applications. For example, in an aircraft engine, a turbine has a turbine blade that is disposed adjacent to a shroud. The clearance between the turbine blade and the shroud varies depending on the temperature of the turbine components. For example, the clearance between the shroud and the turbine blade is greatest when the turbine rotor is cold and gradually decreases as the turbine rotor heats up. It is desirable that a minimum gap or clearance between the turbine blade and the shroud be maintained for operating efficiency and for safe and effective operation of the turbine.
Unfortunately, existing control systems do not accurately respond to varying clearances during different stages of operation. Thus, the existing control systems typically result in reduced performance, inefficiencies, or undesirable wear. In particular, existing clearance measurement systems have a marked tradeoff between accuracy and operating range thus resulting in reduced performance during different stages of operation.
Accordingly, a need exists for providing a clearance measurement system that provides an accurate measurement of clearance between two components over an entire range of operation of an engine. It would also be advantageous to provide a self-calibrating clearance measurement system that could be employed for accurate clearance measurement for parts in operation.